Perspectives in Nutrition, 8th EditionChapter 14 Outline: Water and Major Minerals

After studying this chapter, you will be able to:  

1. Describe the factors that influence water balance and how it is maintained in the body. 2. Discuss how both dehydration and water intoxication develop and how to prevent them.

3. Identify food sources of water and major minerals.

4. Explain the functions of water and major minerals in the body.

5. Discuss the problems with low and high intakes of major minerals and how to avoid inadequate or excessive intakes.

6. Explain the role of nutrition in the prevention and treatment of hypertension.

7. Estimate and evaluate adequacy of dietary calcium intake.

8. Describe the role of nutrition in bone health and in the prevention of osteoporosis.

14.1 WaterA. Water in the Body: Intracellular and Extracellular Fluid

1. Body has no storage site for water; death occurs within a few days with no water2. Water makes up 50 - 75% of body weight, depending on age and body fat content

a. Lean tissue is 73% waterb. Adipose tissue is only 20% water

3. Compartmentsa. Intracellular compartment: inside cells, makes up 2/3 body waterb. Extracellular compartment: outside cells

i. Interstitial fluid: between cellsii. Intravascular fluid: in blood and lymph

4. Fluid contains solutesa. Electrolytes form when salts dissociate in solution to form ionsb. Cations: positively charged ions

i. Intracellular cations: potassium, magnesiumii. Extracellular cations: sodium, calcium

c. Anions: negatively charged ionsi. Intracellular anions: phosphate, sulfate

ii. Extracellular anions: chloride, bicarbonate5. Maintenance of Water Balance

a. Water balance is controlled by electrolyte concentrations, which are regulated by pumping mechanisms that use energy to move ions against a concentration gradient (see Figure 14-3)

b. Water is attracted to ions

c. Osmosis: passive diffusion of water across a semipermeable membrane (cell membrane) from an area of low concentration to an area of high concentration (see Figure 14-4)

d. In cells, water cannot move easily through lipid membranes, but moves through aquaporins, made of proteins

e. Tight regulation of water balance is necessary because shifts in cellular water volume can disrupt function

B. Functions of Water1. Maintenance of blood volume2. Transport of nutrients and oxygen3. Basis for saliva, bile, amniotic fluid4. Lubricates joints5. Solvent for and participant in many metabolic processes6. Temperature Regulation

a. Maintenance of body temperature within a narrow range ensures normal enzyme function

b. Water has high heat capacity (specific heat): resists temperature changes because polar water molecules are strongly attracted to each other, requiring large amount of energy to change state

c. Perspiration and subsequent evaporation releases excess heat, cools the body

7. Waste Product Removala. Most wastes are water soluble and excreted in urineb. Liver converts many fat-soluble compounds into water-soluble

compounds for excretion in urinec. Urine production depends upon

i. Protein intake (i.e., urea excretion)ii. Sodium intake

iii. Fluid intaked. Normal urine output: 1 - 2 L

i. Minimal required urine output: 600 mlii. Low urine output (i.e., concentrated solutes) increases risk for

kidney stones in susceptible peopleC. Water in Foods

1. Beverages and liquid foods2. Fruits and vegetables (75 - 95% water)3. Potatoes, meats (50 - 75% water)4. Jam, honey, crackers, fats (low water)5. Sweetened beverages also supply calories (13 - 22% of total kcal; soft drinks are

single largest source of calories in U.S. diet)a. Liquid calories do not promote satietyb. No compensation by eating lessc. Low nutrient density

6. Caffeine is a mild diuretic, but intakes up to 500 mg/d (4 - 5 c/d of brewed coffee) do not lead to water imbalance or dehydration

7. Alcohol increases urine output by inhibiting antidiuretic hormone, which leads to dehydration

8. Bottled versus tap watera. Bottled water is no safer than tap waterb. Bottled water may not contain fluoridec. Bottled water is more expensive than tap waterd. Producing and disposing of plastic bottles has negative environmental

impactD. Water Needs

1. Individual variances a. Body sizeb. Physical activityc. Environmental conditionsd. Dietary intake

2. AI for total water intake (water from liquids and foods)a. Adult men: 15 cups (13 cups from fluids)b. Adult women: 11 cups (9 cups from fluids)

3. Components of water intakea. Fluidsb. Foodsc. Water is produced as a byproduct of metabolism (1 - 1.5 c/d)

4. Components of water outputa. Urine (600 - 1000 ml/d)b. Skin (450 - 1900 ml)c. Lungs (250 - 350 ml)d. Feces (100 - 200 ml)

5. GI tract is efficient at conserving watera. GI secretions: 32 cb. Diet: 8 - 13 cc. Losses in feces: ½ - ¾ c

6. Kidneys conserve water: reabsorb 97% of filtered water7. Dehydration

a. Causesi. Diarrhea or vomiting

ii. Feveriii. Heavy exerciseiv. Hot weatherv. Dry environments

vi. High altitudesb. Thirst mechanism does not always work well

i. Intense exercise (consume 2.5 - 3 c for every pound of weight lost)

ii. Illnessiii. Infancyiv. Old age

c. Signs of mild - moderate dehydration (see Figure 14-9)i. Dry mouth and skin

ii. Fatigueiii. Muscle weaknessiv. Decreased urine outputv. Deep yellow urine

vi. Headachevii. Dizziness

d. Severe dehydrationi. Concentrated blood

ii. Decreased blood volume and blood pressureiii. Increased heart rate

e. Antidiuretic hormone: released by pituitary gland in response to increased concentration of blood and decreased blood pressure; signals kidneys to reduce urine output

8. Water Toxicitya. Overconsumption of water dilutes blood, leading to hyponatremia (low

serum sodium)b. Symptoms

i. Headacheii. Blurred vision

iii. Muscle crampsiv. Convulsionsv. Death

c. High-risk populationsi. Mental disorders

ii. Infants given extra water or overdiluted formulaiii. Endurance athletes

d. Prevention for endurance athletes: consume sports drinks, which contain electrolytes, instead of plain water

14.2 Overview of MineralsA. General

1. Essential, inorganic elements needed in small amounts in the diet for normal function, growth, and maintenance of body tissuesa. Cannot be synthesized by the bodyb. Health declines when substance is not consumedc. Deficiency symptoms are alleviated by restored intake

2. Classified by needsa. Major (macro) minerals: 100 mg or moreb. Trace (micro) minerals: less than 100 mg

3. Functions of minerals and water (see Figure 14-1)a. Cell metabolism

i. Calciumii. Phosphorus

iii. Magnesiumiv. Zincv. Chromium

vi. Iodidevii. Water

b. Bone healthi. Calcium

ii. Phosphorusiii. Ironiv. Zincv. Copper

vi. Fluoridevii. Magnesium

c. Growth and developmenti. Calcium

ii. Phosphorus iii. Zinc

d. Blood formation and clottingi. Iron

ii. Copperiii. Calcium

e. Nerve impulsesi. Sodium

ii. Potassiumiii. Chlorideiv. Calcium

f. Muscle contraction and relaxationi. Sodium

ii. Chlorideiii. Potassiumiv. Calciumv. Magnesium

g. Antioxidant defensesi. Selenium

ii. Zinciii. Copper

iv. Manganeseh. Water and ion balance

i. Sodiumii. Potassium

iii. Chlorideiv. Phosphorusv. Water

B. Food Sources of Minerals1. Some minerals are most bioavailable from animal sources

a. Calciumb. Ironc. Zinc

2. Some minerals are found mainly in plant sources, although bioavailability may be hindered by plant compoundsa. Potassiumb. Magnesium

3. Factors that affect mineral content of foodsa. Genetic variationsb. Mineral composition of animal feed and medicationsc. Soil and water mineral contentd. Mineral content of fertilizers and pesticidese. Food processing (e.g., equipment, additives, refinement)f. Fortification

i. Salt - iodineii. Some types of orange juice - calcium

iii. Breakfast cereals - variety of vitamins and minerals C. Absorption of Minerals

1. Factors that affect absorption of mineralsa. Physiological need for mineral (higher needs increase absorption)b. Nutrient competition: minerals of same weights and charges may

compete for absorption (e.g., magnesium, calcium, iron, and copper)c. Non-mineral dietary substances

i. Phytic acid (phytate) in wheat grain fiber, although leavening with yeast improves mineral bioavailability

ii. Oxalic acid (oxalate) in leafy green plantsiii. Polyphenols in tea, chocolate, and wine

d. Some vitamins enhance mineral bioavailabilityi. Vitamin C - iron

ii. Vitamin D hormone - calcium, phosphorus, and magnesiume. Gastric acidity: HCl dissolves and maintains minerals in reduced state

D. Transport of Minerals 1. Free form: some can be reactive and/or toxic if unbound2. Bound to proteins

E. Excretion of Minerals1. Urine2. Bile

F. Functions of Minerals1. Water balance2. Transmission of nerve impulses3. Enzyme cofactors4. Components of body compounds (e.g., hemoglobin, bone)

G. Mineral Deficiencies1. Calcium2. Potassium3. Magnesium4. Iron5. Zinc6. Iodide

H. Mineral Toxicity1. Excess supplemental intake may lead to toxicity2. Competition may limit absorption of some minerals3. Supplements may be contaminated (e.g., with lead) - select brands with USP

label

14.3 Sodium (Na)A. General

1. Produced by mining inland salt deposits or evaporating sea water2. Historically valued (root of the word “salary”)3. Used in food processing

a. Flavorings/flavor enhancersb. Preservativesc. Leavening agentsd. Curing agentse. Wetting agentsf. Color preservativesg. Anticaking agents

4. Most North Americans consume excess sodium (2300 - 4700 mg/d)B. Sodium in Foods

1. Sodium chloride a. 40% sodium (1 tsp, or 6 g, provides 2300 mg sodium)b. 60% chloride

2. Food processing (75 - 80% of intake)a. White bread and rollsb. Processed meatsc. Cheesed. Dried and canned soups

e. Tomato saucef. Condiments and saucesg. Seasoned pasta mixesh. Canned and frozen entreesi. Restaurant foods

3. Naturally present in foods (10% of intake); without added salt or food processing, daily sodium intake would be about 500 mg

4. Added in cooking and at table (10 - 15% of intake)5. Softened tap water6. Medicines

C. Sodium Needs1. AI

a. Adults under age 51: 1500 mgb. Adults 51 - 70: 1300 mgc. Adults over 70: 1200 mg

2. DV: 2400 mg3. UL: 2300 mg4. Only 200 mg/d is needed to maintain body functions, but AI is set above needs to

allow for more varied dietD. Storage of Sodium: extracellular fluid sodium content is tightly regulated by kidneysE. Excretion of Sodium

1. Urine2. Feces 3. Perspiration

F. Functions of Sodium1. Absorption of glucose and some amino acids from the small intestine2. Muscle and nerve function: electrical charge resulting from shift in sodium and

potassium ions into and out of cells3. Water balance

a. When excess sodium is ingested, more water is retained until sodium is excreted

b. Faulty sodium excretion by the kidneys, leading to fluid retentioni. Nephrotic syndrome

ii. Congestive heart failureG. Sodium Deficiency

1. Rare due to abundance of sodium in food supply compared to low requirements2. Deficiency (hyponatremia) occurs when losses exceed intake (e.g., excessive

perspiration)a. >2% of body weightb. Perspiration contains only 2/3 the sodium content of blood, but seems

salty due to evaporation of water3. Symptoms

a. Headache

b. Nausea/vomitingc. Fatigued. Muscle crampse. Seizures, coma, death in severe cases

4. Prevention/treatmenta. Salting foodsb. Sports drinks

H. Excess Sodium and Upper Level1. UL: 2300 mg2. 95% of North American adults exceed the UL3. Consequences

a. Hypertension, heart disease, strokeb. Increased calcium losses in urine (although not linked to osteoporosis

risk)c. Increased risk of calcium oxalate kidney stones

4. American Medical Association and World Health Organization call for 50% reduction in sodium content of processed and restaurant foods

5. Reducing sodium intake by 50% will reduce prevalence of hypertension by at least 20% and reduce mortality from coronary heart disease and stroke

6. Food labels help consumers identify sodium content of fooda. Nutrition Facts panelb. Salt-free, sodium-free, low sodium

7. Taste preferences adjust with low-sodium diet8. Table 14-5 provides tips for decreasing sodium intake

14.4 Potassium (K)A. Potassium in Foods

1. Unprocessed foods are best sources of potassium2. Fruits3. Vegetables4. Milk5. Whole grains6. Dried beans7. Meats8. Coffee 9. Salt substitutes (potassium chloride)10. Food additives

B. Potassium Needs1. AI: 4700 mg2. DV: 3500 mg3. Average potassium intakes range from 2100 - 3300 mg/d

C. Storage of Potassium: 95% of potassium is found in cellsD. Excretion of Potassium: urine

E. Functions of Potassium1. Fluid balance2. Transmission of nerve impulses3. Contraction of muscles4. High potassium decreases calcium excretion in urine5. High potassium suppresses renin-angiotensin system and promotes excretion of

excess sodium and waterF. Potassium Deficiency

1. Hypokalemia is life-threatening2. Consequences

a. Weaknessb. Fatiguec. Constipationd. Arrhythmiae. Increased blood pressuref. Increased risk of stroke

3. Causesa. Losses via urine (e.g., due to diuretics)b. Losses via GI tract (e.g., excessive vomiting)c. Low dietary intake (e.g., eating disorders or alcoholism)d. Heavy perspiration

G. Excess Potassium and Upper Level1. Hyperkalemia is also life-threatening2. Causes

a. Not likely due to high dietary intake; excess would be excreted in urineb. Kidney disease impairs excretion

3. Consequencesa. Irregular heartbeatb. Cardiac arrestc. Intestinal upset

14.5 Chloride (Cl)A. General

1. Main anion in the extracellular fluid2. Chlorine (Cl2) is toxic

B. Chloride in Foods1. Table salt2. Processed foods3. Restaurant foods4. Seaweed5. Olives6. Rye7. Lettuce

8. Fruits9. Vegetables10. Salt substitutes

C. Chloride Needs1. AI: 2300 mg, based on AI for sodium2. DV: 3400 mg3. Average intake: 5400 mg

D. Storage of Chloride: extracellular fluid, associated with sodiumE. Excretion of Chloride: urineF. Functions of Chloride

1. Major anion in extracellular fluid; maintains extracellular fluid volume and balance

2. Transmission of nerve impulses3. Component of HCl4. Immune response5. Acid-base balance6. Excretion of CO2 via lungs

G. Chloride Deficiency1. Causes

a. Unlikely due to high salt intakeb. Frequent and lengthy bouts of vomiting coupled with nutrient-poor diet

2. Consequencesa. Weaknessb. Anorexiac. Lethargyd. Disruption of acid-base balance

H. Upper Level for Chloride1. UL: 3.6 g, based on UL for sodium2. Dietary chloride has been implicated along with sodium as a culprit for

hypertension

14.6 Calcium (Ca)A. Calcium in Foods

1. Dairy products are most bioavailable dietary source of calcium, provide ½ calcium in American diets

2. White bread, rolls, crackers3. Leafy greens (e.g., collards, kale, turnip greens), although bioavailability in some

foods is limited by oxalic acid4. Broccoli5. Calcium-fortified foods (e.g., orange juice, breakfast cereals) 6. Canned fish with bones7. Soybean curd made with calcium carbonate

B. Calcium Needs

1. AIa. Adults up to age 50: 1000 mgb. Adults 51+: 1200 mgc. Adolescents: 1300 mg

2. DV: 1000 mg3. Average intake is adequate for men, but inadequate for women4. Calcium supplements are helpful for those with restricted calorie intakes and

those who avoid dairy productsa. Made of calcium salts

i. Calcium carbonate (40% calcium)ii. Calcium citrate: better for those with low stomach acid

iii. Calcium gluconate (9% calcium)b. May contain vitamin D to boost calcium absorptionc. Dose should be no more than 500 mg at a timed. Consuming with meals improves absorption due to higher acid

concentration in stomache. Interactions with other minerals; do not take calcium supplements at the

same time as other mineral supplementsi. Zinc

ii. Ironiii. Magnesium

f. Contamination with leadi. Most likely in supplements made with bone meal or oyster shell

ii. Look for USP label to lessen risk of contaminationC. Calcium Absorption

1. Factors that increase calcium absorptiona. Active vitamin D hormone (in upper GI tract)b. Increased need (e.g., infancy, pregnancy), absorption increases to 75%c. Lactose and other sugarsd. Protein

2. Factors that decrease calcium absorptiona. Ageb. Phytic acidc. Oxalic acidd. Excessive phosphoruse. Polyphenols f. Vitamin D deficiencyg. Diarrheah. Fat malabsorption: fatty acids bind to calcium to form unabsorbable

soaps D. Calcium Transport

1. Free ionized calcium2. Bound to proteins

E. Calcium Storage1. 99% in skeleton and teeth2. Small, regulated amount in blood

F. Calcium Regulation1. Because of tight regulation, blood calcium is a poor indicator of calcium status2. When blood calcium is low, parathyroid gland releases parathyroid hormone

(PTH):a. Works with 1,25 (OH)2 vitamin D to increase kidney’s reabsorption of

calciumb. Increases calcium absorption by increasing synthesis of 1,25 (OH)2

vitamin Dc. Works with 1,25 (OH)2 vitamin D to increase release of calcium from

bones3. When blood calcium is high, release of PTH falls

a. Urinary calcium excretion increasesb. Synthesis of 1,25 (OH)2 vitamin D decreases, leading to decreased

absorption of calciumc. Thyroid gland secretes calcitonin, which blocks calcium loss from bones

G. Calcium Excretion1. Urine2. Skin3. Feces (intestinal secretions)

H. Functions of Calcium1. Bone Development and Maintenance

a. Calcium and phosphorus are main bone minerals, form hydroxyapatite, which imparts strength and resilience

b. Collagen forms bone matrix, allows absorption of impactc. Cortical boned. Trabecular bone

i. Site of mineral exchangee. Remodeling: continuous building, breaking down, and replacing bone

i. Repairs damaged and brittle areasii. Allows withdrawal of stored minerals

iii. Bone mass declines 25% with aging, or more for women with low estrogen (e.g., menopause, amenorrhea, oophorectomy) because estrogen inhibits osteoclast activity

f. Other nutrients involved in bone metabolismi. Magnesium

ii. Potassiumiii. Sodiumiv. Fluoridev. Vitamin K

vi. Sulfur

2. Blood Clotting: calcium ions participate in formation of fibrin3. Transmission of Nerve Impulses to Target Cells4. Muscle Contraction

I. Potential Health Benefits of Calcium1. Bone health2. Protection against colon cancer3. Protection against some forms of kidney stones4. Decreased blood pressure5. Possible link between calcium intake, metabolism, and body weight;

epidemiological evidence is not strongly supported by clinical trials6. May reduce risk for high blood pressure during pregnancy in women with low

calcium intakeJ. Upper Level for Calcium

1. UL: 2500 mg, based on increased risk of kidney stones at higher intakes2. High blood calcium is usually the result of hyperparathyroidism (overproduction

of PTH, usually caused by tumor) or high supplemental doses of calcium 3. Consequences of excessive blood calcium

a. Calcification of kidneys and other organsb. Irritabilityc. Headached. Kidney failuree. Kidney stonesf. Decreased absorption of other minerals

14.7 Phosphorus (P)A. General

1. Major component of bones and teeth2. Glowing material 3. Required by every body cell

B. Phosphorus in Foods1. Milk2. Cheese3. Meat4. Bakery products5. Cereals 6. Bran7. Nuts8. Fish 9. Food additives (may not be included in nutrient databases)10. Nutrients used for fortification

C. Phosphorus Needs1. RDA: 700 mg2. DV: 1000 mg

3. Average intake: 950 - 1650 mgD. Storage of Phosphorus

1. 80% found in bones and teeth as a component of hydroxyapatite2. Extracellular fluid3. Body cells

E. Excretion of Phosphorus: urineF. Functions of Phosphorus

1. Major component of bones and teeth2. Main intracellular anion (HPO4

2- or H2PO4-)

3. Component of ATP and creatine phosphate4. Component of DNA and RNA5. Component of phospholipids in cell membranes6. Takes part in enzyme and cellular message systems (phosphorylation activates

many hormones and enzymes)7. Regulation of acid-base balance8. Possibly protective against hypertension

G. Phosphorus Deficiency1. Rare2. Consequences

a. Bone lossb. Decreased growthc. Poor tooth developmentd. Symptoms of rickets due to insufficient bone mineralizatione. Anorexiaf. Weight lossg. Weaknessh. Irritabilityi. Stiff jointsj. Bone pain

3. High-risk populationsa. Premature infantsb. Alcoholicsc. Older adults with nutrient-poor dietsd. Chronic diarrhea or weight losse. Frequent use of aluminum-containing antacids (bind phosphorus in small

intestine)H. Toxicity and Upper Level for Phosphorus

1. Rare2. Hyperphosphatemia is usually due to compromised kidney function3. Consequences: calcium-phosphorus deposits in body tissues4. UL: 3 - 4 g, based on development of high blood [P]

14.8 Magnesium (Mg)

A. Magnesium in Foods1. Component of chlorophyll; richest sources are plant foods

a. Green leafy vegetablesb. Broccolic. Squashd. Beanse. Nutsf. Seedsg. Whole grainsh. Chocolate

2. Animal products supply some Mga. Milkb. Meats

3. Hard tap water4. Magnesium oxide (in supplements) is not well absorbed

B. Magnesium Needs1. RDA

a. Adult men (age 19 - 30): 400 mgb. Adult women (age 19 - 30): 310 mgc. Needs slightly increase beyond age 30

2. DV: 400 mg3. Average intakes are 80% RDA

C. Storage of Magnesium1. Bones (about 50%)2. Other tissue (particularly muscle)

D. Excretion of Magnesium: kidneysE. Functions of Magnesium

1. Stabilizes ATP by binding phosphate groups2. Cofactor for more than 300 enzymes that utilize ATP

a. Energy metabolismb. Muscle contractionc. Protein synthesis

3. Required for activity of cellular sodium-potassium pump4. DNA and RNA synthesis5. Role in calcium metabolism, contributes to bone structure and mineralization6. Nerve transmission7. Heart and smooth muscle contraction8. Insulin release from pancreas9. Insulin action on cells10. Decreased blood pressure due to vasodilation11. Prevention of arrhythmias12. Protective against gallstone formation

F. Magnesium Deficiency

1. Consequences, likely due to impaired function of Na/K pumpa. Irregular heartbeatb. Weaknessc. Muscle spasmsd. Disorientatione. Nauseaf. Vomitingg. Seizuresh. Decreased PTH release, resulting in low blood calciumi. Blunted action of 1,25 (OH)2 vitamin Dj. Increased risk of metabolic syndrome

2. Slow to develop due to body storage3. Causes

a. Excessive GI tract losses (e.g., prolonged diarrhea or vomiting)b. Excessive urinary losses (e.g., use of diuretics)c. Alcoholismd. Poorly controlled diabetese. Low dietary intakef. Heavy perspiration

G. Upper Level for Magnesium1. UL: 350 mg from supplement and other nonfood sources (e.g., antacids or

laxatives)2. Causes

a. Excessive supplementationb. Chronic antacid or laxative usec. Kidney failure

3. Consequencesa. Weaknessb. Nauseac. Slowed respirationd. Malaise, coma, death

4. High-risk population: older adults, due to declines in kidney function

14.9 Sulfur (S)A. Sources

1. Protein-rich foods (component of methionine and cysteine)2. Preservative used to protect color of dried fruit and white wines

B. Requirements1. No AI or RDA established because of ample consumption from protein foods2. No UL established, no toxicity symptoms

C. Functions1. Synthesis of sulfur-containing compounds2. Stabilize protein structure

3. Acid-base balance

14.10 Global Perspective: Water for EveryoneA. Water supply

1. Average per capita daily water use in U.S. and Europe = 52 - 160 gallons2. Minimum daily clean water need per person (United Nations): 5 ½ gallons3. In addition to personal water usage, water is also needed for agriculture (70% of

world’s water consumption), energy production, and industry4. Millions of people rely on water for income and food production (e.g., fishing,

farming)5. Inadequate water supply leads to poverty, malnutrition, and illness6. 1 in 3 people worldwide faces water shortage due to arid climate or lack of

infrastructure7. Inequitable water distribution may cause civil unrest

B. Water sanitation1. Contamination with sewage, herbicides, pesticides, and toxins causes diseases

(e.g., diarrheal disease), which lead to death, especially among malnourished children

2. Water purification and wastewater treatment are needed

14.11 Medical Perspective: Hypertension and NutritionA. General

1. 1 in 3 adults has hypertension2. Measurement of blood pressure

a. Systolic: pressure in arteries when heart contractsb. Diastolic: pressure in arteries when heart relaxes

3. Classifying blood pressure (see Table 14-6)a. Normal: <120/<80b. Prehypertenion: 120 - 139/80 - 89c. Hypertension, stage 1: 140 - 158/90 - 99d. Hypertension, stage 2: ≥160/≥100

B. Causes of Hypertension1. Secondary hypertension (5 - 10% of cases)

a. Kidney diseaseb. Liver diseasec. Diabetes

2. Primary hypertensiona. Actual cause is not fully knownb. Develops over a period of years as arteries narrow and harden

(arteriosclerosis)c. Endothelial cells release vasoconstrictors in response to arterial damage

d. Increased production of renin by kidneys, leading to increased angiotensin II, a powerful vasoconstrictor that triggers sodium and water retention

C. Risk Factors for Hypertension1. Age: 90%+ over age 55 develop hypertension2. Race: African-Americans develop hypertension more often and at younger age

than whites 3. Obesity: increased fat mass adds blood vessels, increasing heart’s workload4. Diabetes: elevated insulin increases sodium retention; 65% of diabetics also have

hypertensionD. Effects of hypertension

1. Damage to arteries2. Heart attack3. Stroke4. Kidney failure5. Vision loss

E. Lifestyle Modifications to Prevent and Treat Hypertension1. Many recommendations for lowering hypertension are also part of Dietary

Guidelines2. Modest weight loss (10 lbs) for overweight person3. DASH eating plan: high in fruits, vegetables, low-fat dairy; low in sodium and

saturated and total fat4. Moderate physical activity, particularly aerobic exercise 5. Improve insulin sensitivity6. Control alcohol intake7. Control sodium intake

F. Minerals, Phytochemicals, and Hypertension1. Sodium

a. Intersalt study: as urinary sodium excretion increases, blood pressure increases

b. Salt sensitivityi. Only 25-50% of people experience high blood pressure with

high salt intakeii. Trial of sodium restriction is only way to determine salt

sensitivityiii. African-Americans, overweight people, those with diabetes, and

the elderly are more likely to be salt sensitive2. High potassium, low sodium diet offers best protection against hypertension3. High calcium linked to lower blood pressure4. High magnesium linked to lower blood pressure5. High fiber linked to lower blood pressure6. Dark chocolate (6 g/d) causes modest reduction in blood pressure due to

polyphenols that cause vasodilation

7. Caffeine temporarily increases blood pressure, but chronic intake is not associated with increased blood pressure

G. The Dietary Approaches to Stop Hypertension (DASH) Diet1. Food plan

a. Grains: 6 - 8 servings/d (emphasize whole grains)b. Vegetables: 4 -5 servings/dc. Fruits: 4 - 5 servings/dd. Fat-free or low-fat milk products: 2 - 3 servings/de. Lean meats, poultry, and fish: 6 or less servings/weekf. Nuts, seeds, and legumes: 4 - 5 servings/weekg. Fats and oils: 2 - 3 servings/dh. Sweets and added sugars: 5 or less per week

2. Nutrient goalsa. Low in fat (27% of kcal)b. Low in saturated fat (6% of kcal)c. Moderate in protein (18% of kcal)d. Moderate in carbohydrates (55% of kcal)e. Low in cholesterol (150 mg/d)f. Low in sodium (2300 mg/d is effective, 1500 mg/d shows better

reductions in blood pressure)g. High in potassium (4700 mg/d)h. High in calcium (1250 mg/d)i. High in magnesium (500 mg/d)j. High in fiber (30 g/d)

3. Works as well as medications for those with hypertension4. Health benefits of DASH diet

a. Reduced blood pressureb. Cancer preventionc. Heart disease prevention

H. Drug Therapy for Hypertension1. Usually initiated when blood pressure exceeds 140 mmHg systolic and/or 90

mmHg diastolic on 3 or more occasions2. Diuretics: increase water and salt excretion; may increase potassium excretion

(e.g., furosemide and hydrochlorothiazide)3. Beta-blockers: slow heart rate and decrease force of heart contraction (e.g.,

metropolol)4. Angiotensin-converting enzyme (ACE) inhibitors: reduce conversion of

angiotensin I to angiotensin II in the lung, leading to vasodilation (e.g., captopril)5. Calcium channel blockers: prevent calcium from entering cells of heart and blood

vessels, leading to vasodilation (e.g., nifedipine)

14.12 Medical Perspective: OsteoporosisA. General

1. Low calcium intake is most common cause; calcium is withdrawn from bone to maintain blood calcium levels

2. Develops over many years3. Osteopenia: low bone mass caused by vitamin D deficiency, medications, cancer,

anorexia nervosa, or other conditions4. Diagnosis of osteoporosis occurs when bone mass has declined to the extent that

bone strength is compromised and bones are likely to break (e.g., hip, wrist, vertebrae)

5. Kyphosis (dowager’s hump): compression fractures in vertebrae lead to loss of height

6. 8 million women and 2 million men suffer from osteoporosis; 34 million have low bone mass

7. Ethnic/racial disparitya. African-Americans are least likely to develop osteoporosisb. Highest rates in Caucasian and Asian populations

8. Risk factors for osteoporosisa. Family historyb. Small, thin skeletal framec. Low peak bone massd. Advancing agee. Caucasian or Asian ancestryf. Menopauseg. Amenorrheah. Oophorectomy: removal of ovariesi. Smokingj. Low calcium intakek. Vitamin D deficiencyl. Low physical activitym. Excessive alcohol consumptionn. Diseases that impair nutrient absorption, metabolism, or utilization of

bone-forming nutrients or increase their excretion (e.g., cystic fibrosis, anorexia nervosa, type 1 diabetes mellitus, inflammatory bowel disease, celiac disease, multiple sclerosis, epilepsy)

o. Some medications (e.g., glucocorticoids) B. Osteoporosis Diagnosis

1. Dual energy X-ray absorptiometry (DEXA) bone scan measures ability of bone (spine, hips, and whole body) to block the path of radiation; compare with bone density of person at peak bone density

2. Peripheral DEXA or ultrasound: measure bone density at one site (e.g., wrist or heel); faster than DEXA, but not as accurate

C. Osteoporosis Prevention and Treatment1. Consume ample calcium, vitamin D, phosphorus, magnesium, vitamin K, and

potassium

2. Vitamin D requirements may be much higher than current AI for older adults and those with osteopenia or osteoporosis

3. 1200 mg/d calcium + 800 IU/d vitamin D4. Physical activity, including weight-bearing activity; also improves balance and

strength to reduce risk of falling5. Smoking cessation6. Limited alcohol intake7. Moderate intakes of caffeine, sodium, and protein to decrease calcium excretion

D. Drug Therapy for Osteoporosis Prevention1. Decrease of more than 1 ½ inches from pre-menopausal height is a sign of

significant bone loss among postmenopausal women2. Estrogen: slows osteoclast activity, but may increase risk of CVD and certain

cancers3. Bisphosphonates: bind to hydroxyapatite crystals and osteoclasts to slow bone

resorption (e.g., alendronate and ibandronate)4. Selective estrogen receptor modulators (SERMS): increase utilization of existing

estrogen to slow osteoclast activity (e.g., raloxifene)5. Calcitonin: inhibits osteoclast activity and bone resorption6. PTH: stimulates osteoblast activity and new bone formation